Owner's manual
Table Of Contents
- DMT345/346 USER'S GUIDE
- TABLE OF CONTENTS
- GENERAL INFORMATION
- PRODUCT OVERVIEW
- INSTALLATION
- OPERATION
- Getting Started
- Display/Keypad
- MI70 Link Program for Data Handling
- Serial Line Communication
- LAN Communication
- Communicating with a Transmitter in POLL Mode
- General Settings
- Serial Output Settings
- Data Recording
- Analog Output Settings
- Operation of Relays
- Sensor Functions
- MODBUS
- MAINTENANCE
- CALIBRATION AND ADJUSTMENT
- TECHNICAL DATA
- EXAMPLE INSTALLATION OF DMT346
- CALCULATION FORMULAS
- MODBUS REFERENCE
Chapter 2 ___________________________________________________________ Product Overview
VAISALA ________________________________________________________________________ 21
Basic Features and Options
- Dewpoint measurement with AutoCal and sensor purge features
- Sensor warming in high humidities
- Two analog outputs and a serial interface, optional third analog output
- Installation accessories
- DMT345: mounting flange
- DMT346: cooling set for high temperature applications.
- User friendly display and keypad interface (optional)
- Different sensor protection options and probe cable lengths
- Support for Modbus serial communications protocol
- USB connectivity for service connections via the optional
USB-RJ45 cable
- Optional modules:
- Galvanic isolation for outputs
- Power supply module for AC mains power
- RS-422/485-module
- LAN and WLAN interfaces
- Data logger module with real time clock
- Additional analog output module
- Alarm relay module
Operating Principle
The DMT345/346 transmitter incorporates the Vaisala DRYCAP®
sensor together with a combined temperature measurement with a PT100
resistive temperature sensor. The operating principle of the DRYCAP®
sensor is based on the changes in capacitance as its thin polymer film
absorbs water molecules.
The DMT345/346 transmitter measures water vapor directly and gives
thus accurate results of moisture in the process. In DMT346, the sensor is
cooled down with a cooling set which makes it possible to use a polymer
sensor in very high temperatures, for example, +100 ... +350 °C. With
this technique, no complicated sampling systems are needed. The cooling
set is thermally isolated from the process itself. The temperature of the
sensor is cooled down which increases the sensor saturation rate.
Sensor saturation rate and temperature are then measured, and the
transmitter calculates the dewpoint and the mixing ratio on the basis of
those readings.
Note that for DMT346, SSR and temperature values do not represent the
process itself as they are measured after cooling. Dewpoint and mixing
ratio, however, are independent of temperature and remain unchanged.
The dewpoint measurement range is -25 ... +100 °C.